These are a pair of .45 caliber elephant rifle cartridges based on the long .375 H&H Magnum case necked-up to accept .458" bullets. Ballistically, the .450 Watts Magnum and .458 Lott are essentially identical. The .458 Winchester Magnum is also based on the .375 H&H case, but shortened to work in a standard (.30-06 length) bolt action rifle. The Watts and Lott cartridges both require rifles with a long (.375 H&H length) "magnum" action.

Because the .458 Winchester Magnum is essentially a shortened version of these longer .375 H&H based rounds, .458 Win. Mag. cartridges can safely be fired in both .450 Watts and .458 Lott rifles. (Since the .450 Watts is a wildcat, and not a standardized caliber, this may not be true of all .450 Watts rifles and chambers.) However, the .450 Watts and .458 Lott cartridges are not interchangeable with each other.

The .458 Lott was standardized by A-Square, who produces both rifles and ammunition in the caliber, as well as brass and bullets for reloaders. Hornady also offers factory loaded ammunition in .458 Lott, and supplies brass and bullets to reloaders.

A-Square factory loads claim a MV of 2380 fps and ME of 5848 ft. lbs. from their Triad of 465 grain bullets. Hornady loads a 500 grain RN bullet at a MV of 2300 fps and ME of 5872 ft. lbs. At 100 yards the velocity of the Hornady load is 2022 fps and the energy 4537 ft. lbs.; at 200 yards the velocity is 1776 fps and the remaining energy 3502 ft. lbs.

According to the sixth edition of the Hornady Handbook of Cartridge Reloading 65.3 grains of H322 powder will drive their 350 grain RN or FP bullets to a MV of 2300 fps. This would be a useful load for any North American big game. A maximum load of 79.8 grains of H322 will drive the same bullets to a MV of 2600 fps.

The Hornady 500 grain RN (soft point) and FMJ-RN (solid) bullets can be driven to a MV of 1900 fps by 67.1 grains of H335 powder. A maximum load of 79.3 grains of H335 will drive those bullets to a MV of 2200 fps. These Hornady loads used Hornady brass and Win. WLRM primers, and were tested in a 24" barrel.

Note: A full length article about the .450 Watts Mag. and .458 Lott can be found on the Rifle Cartridge Page.